A driving device for a vehicle, for example, a driving device for a railway vehicle includes traction electric motors provided respectively in a truck near wheels and a controlling device that controls these traction electric motors. Output shafts of the traction electric motors are connected to the wheels via series of gears, and drive the wheels. The driving electric motor conventionally has a self-ventilation cooling structure in which cooling is performed by flowing external air inside thereof, and bearings supporting the rotation shafts are lubricated by lubricant grease.
Since the electric motors for the railway vehicle are installed in the trucks, there are quite a few cases in which they are exposed to foreign substances from outside such as dust, rain, snow, and the like. Due to this, the electric motors require periodic maintenance that accompanies disassembly, and cleaning of the insides of the devices that have been contaminated by the foreign substances from the outside is highly recommended.
On the other hand, needs to elongate a maintenance cycle, that is, needs for electric motors which can reduce the number of times of maintenance are increasing. In order to meet such needs, a development of a fully enclosed type electric motor is under progress.
Each of such electric motors includes a stator core provided on an inner circumferential side of a cylindrical frame and having a stator coil, and a bracket and a housing attached to both sides of the frame and configuring a sealed casing, and a bearing is internally provided respectively in these bracket and housing. A rotor shaft extends inside the sealed casing, and both end portions thereof are rotatably supported by the bearings. A rotor core is attached to a center portion of the rotor shaft, and is positioned at an inner side of the stator core. Further, a partition plate is attached to each end portion of the rotor shaft inside the sealed casing, and an outer periphery of each partition plate forms a labyrinth seal portion.
The electric motors configured as described above are the fully enclosed type motors, and since external air does not flow inside thereof, the interior of the motor is not contaminated by dust, so labor therefore can be saved by omitting the disassembly of the electric motors for cleaning the insides thereof.
However, since the bearings are lubricated by grease filled in bearing portions, the lubricant grease deteriorated by the operation, and the lubricant grease needs to be renewed. The renewal of the lubricant grease needs to be performed after having disassembled the electric motors, by which large amounts of labor and time were required.
For example, a rotor suspending jig is set to each shaft end of the rotor shaft, and after having detached the bracket and the housing from the frame, an entirety of the rotor in a state of still having the bearings attached is drawn out from the frame in an axial direction. Thereafter, the bracket and the housing are drawn out from the rotor, and the grease of the bearing portions is replaced with a new one. After replacing the grease, the rotor is inserted into the frame in an opposite order and is coaxially aligned, and thus the electric motor is reassembled.
As aforementioned, although the cleaning of the inside due to contamination becomes unnecessary by forming the electric motors as the fully enclosed type, the disassembly and reassembly of the electric motors need to be performed periodically in order to renew the bearing lubricant grease, and this is requiring large amounts of labor and time. Further, replacements of the bearings become necessary due to long-term use, wear, and the like, and at such occasions, the electric motors need to be disassembled.